From the Mediterranean to the Pacific: re-circumscription towards Notelaea s.l. and historical biogeography of a generic complex in Oleinae (Oleaceae)

Tackling the complicated infrafamilial classification of the economically important Oleaceae requires a piecemeal approach that addresses generic circumscriptions. Here, focusing on the distinct clade formed by the generic complex Nestegis, Notelaea, Osmanthus, Phillyrea and Picconia in subtribe Oleinae, we aim to elucidate their boundaries and relationships and to evaluate their biogeographic history in light of their peculiar disjunct distribution in the Macaronesian, Mediterranean and Pacific regions. On the basis of phylogenomic data from plastid and nuclear DNA of an extensive sampling, the results show six subclades in this generic complex, which are also geographical segregates found in Australia (Notelaea), Hawaiian Islands (Nestegis sandwicensis), Macaronesia (Phillyrea and Picconia), Mediterranean Region (Phillyrea), New Caledonia (Osmanthus section Notosmanthus) and New Zealand (Nestegis s.s.). Accounting for broad morphological overlaps in this clade, we recognize three genera (Phillyrea, Picconia and Notelaea s.l.), subsuming all Pacific taxa under Notelaea. Molecular dating and biogeographic analyses indicate that this clade originated in Eurasia during the Early Miocene (mean 23.2 Mya, 95% HPD: 23.8-14.7). Finally, dispersal (rather than continental vicariance) is probably the main explanation for the global, disjunct distribution of this group, with island-hopping and local extinction as the hallmarks of its evolutionary history.

Automated summary

The complicated infrafamilial classification of Oleaceae, an economically important family, requires a gradual approach. This study focuses on the clade formed by Nestegis, Notelaea, Osmanthus, Phillyrea, and Picconia in subtribe Oleinae and aims to determine their boundaries, relationships, and biogeographic history. Phylogenomic analysis using DNA data reveals six subclades within this clade, which are geographically segregated in Australia, Hawaiian Islands, Macaronesia, Mediterranean Region, New Caledonia, and New Zealand. The study suggests that this clade originated in Eurasia during the Early Miocene and their global, disjunct distribution is mostly due to dispersal rather than continental vicariance.